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RE: Question on XSBI


That is what I suspected. I agree that the A1/A2 alignment is probably 
automatic coming out of the WIS. I was actually more concerned about what 
happens in the receive direction of an ELTE transponder, where the output 
of the line side 16:1 demux would be fed into the LW-4 PMA. The output of 
the 16:1 demux is not A1/A2 aligned. I guess a additional framing layer 
would be required between the demux and the LW-4 PMA in order to perform 
the necessary A1/A2 alignment ?
Or maybe no one is considering developing an ELTE with an LW-4 interface ?

Gary ....

At 05:19 PM 2/22/01, Tom Alexander wrote:
>Hi, Gary,
>In the transmit case, the WIS will send data on the XSBI with the proper 
>A1/A2 alignment such that the LW-4 PMA will not need to do framing. This 
>is actually automatic (you have to go to some trouble to NOT do this!), 
>but Clause 50 specifies this anyway for completeness. In the receive case, 
>the the XSBI receive path into the WIS does not require any A1/A2 
>alignment; however, the LW-4 PMA - but not the serial PMA - will have to 
>do basic A1/A2 framing so that it can align the incoming streams.
>Best regards,
>- Tom Alexander
>-----Original Message-----
>From: Gary Nicholl [mailto:gnicholl@xxxxxxxxx]
>Sent: Thursday, February 22, 2001 12:52 PM
>To: stds-802-3-hssg@xxxxxxxx
>Subject: Question on XSBI
>I have been reading through clause 53 and it triggered a question on XSBI.
>Are the 16 data bits of the XSBI interface in any way aligned with the byte
>boundaries of the SONET frame ? I don't believe that any alignment is
>specified in the OIF SFI-4 spec.  If this is the case does it mean that the
>LW4-PMA has the ability to locate the SONET A1/A2 frame boundary on any one
>of 16 possible bit alignments within the XSBI interface ?
>Gary .....